The ELECTRORETINOGRAM (ERG) is an important diagnostic tool in ophthalmology, but it is at times misunderstood. I hear regularly of patients with symptoms of retinal dysfunction who have had fluorescein angiography and sometimes magnetic resonance imaging, while an ERG was deferred for fear that the test was somehow difficult or expensive. This myth—for it is a myth—is unfortunate. The ERG takes less than an hour to perform, costs about the same as other ophthalmic diagnostic tests, and is no more disturbing to the patient than fluorescein angiography or perimetry. Even more critical, it is the most direct and objective test in ophthalmology for evaluating the function of the retina. How else can you find out, without subjectivity and without injections, how well the rods and cones are working, or whether a disease is limited to the macula?
The conventional ERG is performed by placing an electrode on the eye and
Marmor MF. The ERG Is Alive and Well. Arch Ophthalmol. 1995;113(11):1371-1372. doi:10.1001/archopht.1995.01100110031019